refactor testcase layer mechanism:

1, autotest testsuite layer
2, performance test

tests/testsuites/create_users.yml

@@ -1,17 +1,18 @@
-- config:
+config:
     name: create users with uid
     variables:
         device_sn: ${gen_random_string(15)}
     base_url: "http://127.0.0.1:5000"
 
-- test:
-    name: create user 1000 and check result.
-    testcase: testcases/create_and_check.yml
-    variables:
-        uid: 1000
+testcases:
+    create user 1000 and check result.:
+        testcase: testcases/create_and_check.yml
+        weight: 2
+        variables:
+            uid: 1000
 
-- test:
-    name: create user 1001 and check result.
-    testcase: testcases/create_and_check.yml
-    variables:
-        uid: 1001
+    create user 1001 and check result.:
+        testcase: testcases/create_and_check.yml
+        weight: 23423
+        variables:
+            uid: 1001